This invention is directed to a method and apparatus for treating a fabric which is simultaneously embossed and decorated and, in particular, to a method and apparatus for treating a velvet-like fabric.
The process of embossing fabrics is known in the art. Embossed fabrics have raised or projected figures or designs in relief on fabric surfaces. Embossed surfaces are usually produced by passing the fabric through engraved, heated rolls under heavy pressure to give a raised effect. The fabric may be passed through two rolls, one of which is engraved and the other being smooth, or both rolls may be engraved in such a manner that when the rolls are synchronized, the indentations in one roll at the point of embossing cooperate with protuberances on the other roll.
The method of heat transfer printing is also well known in the art. This is a method of printing fabric made of polyester or other thermoplastic fibers with disperse dyes. The design is transferred from pre-printed paper onto the fabric by contact heat. Having no affinity for paper, the dyes are absorbed by the fabric. To complete the transfer, the preprinted paper must be in contact with the fabric for a sufficiently long residence time, i.e. the time during which the fabric is between the rolls, although the length of residence time may be reduced if the pressure on the preprinted paper and fabric is increased. The method is capable of producing well defined, clear prints.
Processes for simultaneously embossing and transfer printing to fabrics are known in the art as well. In U.S. Pat. No. 1,744,829 and U.S. Pat. No. 1,895,243, the simultaneous printing and embossing of cellulosic fabrics is disclosed. A transfer dye sheet and cellulosic fabric are simultaneously passed between one embossed and one smooth roll under high pressure with the transfer sheet passed through directly next to the engraved roll. No printing or embossing occurs at the portions of the fabric which pass between the smooth roll and the engraved portions of the engraved roll because the engraving is of a sufficient depth that the fabric does not contact the embossing roll at the engraved portions. Either the transfer printing sheet or the fabric is moistened prior to passing between the rolls. Both patents teach that heating the rolls increase the transferability of the dye in the transfer sheet to the fabric. The simultaneous transferring and embossing operation allows the printing to be transferred directly to the portion of the fabric which has been embossed, i.e., the portion of the fabric pressurized by the protuberances on the engraved roll.
The disadvantages of the apparatuses and methods taught by these patents is that they produce less than satisfactory results if the fabric to be embossed and decorated possesses depth, as in velvet-like fabrics, instead of ordinary flat woven and knit fabrics. Velvet-like fabrics and methods of producing them are known in the art. Velvet-like fabrics include a base and a surface region defined by a short, but usually dense, pile formed of fibers. Velvet-like fabrics may be knit, woven or flocked. For example, a woven velvet-like fabric may be made by producing a double-cloth structure woven face to face, with the pile ends interchanging between the two cloths. The two fabrics are cut apart by a traversing knife, producing two fabrics with a cut-pile surface. In another method, pile ends are lifted over cutting wires which are inserted in the same manner as the filling and the pile is cut as the wire is withdrawn.
Flock fabrics are another type of velvet-like fabrics which are produced by a process known as "flocking" in which adhesive is printed or coated on a fabric, and finely cut fibers are either adhered to or embedded in the fabric by means of dusting, air-blasting or electrostatic attraction. The finely cut fibers remain adhered to or embedded in the fabric at those portions of the fabric which were printed and coated with adhesive. The result is a velvet-like fabric. In a variation known as flock printing, only selected portions of the fabric are printed or coated with adhesive and, after the finely cut fibers are adhered to or embedded in the fabric, the fibers not secured by adhesive are removed by mechanical action.
In simultaneously embossing and decorating a pile fabric such as a velvet-like fabric, the fiber ends not attached to the fabric base, or embedded in the adhesive if the fabric is a flock fabric, may not be erect and so the fibers may be laying down prior to the embossing step, particularly if the fabric has been rolled-up. The contrast between the embossed and non-embossed portions will thus be reduced if the non-embossed portions are flat. Thus, a velvet-like fabric which is simply processed with the embossing and decorating methods taught in the prior art will have a less than satisfactory contrast in color and contour between the embossed and non-embossed area.
Additionally, known methods for simultaneously embossing and decorating are less than completely satisfactory if the fabric is a thermoplastic fabric and the decorating step is transfer printing of dye. Thermoplastic fabrics are fabrics at least the surface region of which are essentially made from synthetic materials such as nylon, polyester and acrylic which soften or "plasticize" when heated. Such surface regions are capable of embossing by the application of heat and pressure. One problem with known methods is due to the limited residence time of the fabric between the rolls during the step of embossing and printing. Not enough dye may be transferred to the fabric since the residence time may be insufficient to heat the fabric and pre-printed paper to the required temperature and transfer enough dye to the fabric. Yet another problem is that thermoplastic fabrics do not "soak up" dyes readily in the transfer printing process when the time to transfer the dye is brief, and much of the dye will rub off the fabric after the simultaneous step of embossing and printing.
Accordingly, a method and apparatus for simultaneously embossing and decorating a thermoplastic velvet-like fabric which overcomes the problems outlined above is desired.